FRIDAY, Oct. 4 (HealthDay News) -- The large amount of money that Medicare spends on PSA screening for prostate cancer provides little benefit for older men, according to a new study.

Over three years, the Medicare fee-for-service program spent more than $450 million a year on PSA (prostate-specific antigen) screenings, one-third of which was for men over age 75, said the researchers at Yale University's Cancer Outcomes, Public Policy and Effectiveness Research Center.

But most prostate cancers are slow-growing and unlikely to become a threat to older men, noted the researchers, who followed prostate cancer-free, older male Medicare beneficiaries. The investigators also noted that widespread PSA screening may lead to unnecessary biopsies, which can be uncomfortable and even harmful.

In 2012, the U.S. Preventive Services Task Force stopped recommending PSA screening for men of any age. However, Medicare continues to reimburse for this test and follow-up procedures.

The benefits of PSA screening and treatment are not clear, the study authors said. While men living in high-spending regions were more likely to be diagnosed with localized cancers, they were not significantly less likely to be diagnosed with metastatic (spreading) cancer. This suggests that spending more on prostate cancer screening might identify more localized tumors, but may not necessarily reduce the rate of metastatic cancers.

The study, published in the Oct. 4 issue of the journal Cancer, also found wide variation in the cost of prostate cancer screenings in different regions of the country, ranging from $16 to $65 per Medicare beneficiary. Most of the variation was not due to the cost of the PSA test itself, but rather to differences in the costs of follow-up tests.

"More than 70 percent of prostate cancer screening-related costs were due to follow-up procedures," study author Xiaomei Ma said in a Yale news release. "Our results suggest that the overall cost of prostate cancer screening may be heavily influenced by how urologists choose to respond to the result of a PSA test, more so than the use of the PSA itself."